The invention in general relates to a device for processing optical waves. More specifically, the invention relates to a monolithically integrated Optical Wavelength and Waveform Manipulator (OWWM).
Optical networking is now being used for digital communication in networks. Optical networks for digital communication have lesser electromagnetic interference and lower power requirements as compared to the existing electrically wired networks. Further, the bandwidth capacity of optical networks has improved due to the development of optical devices that handle multiple wavelength signals. Examples of optical devices include a waveform add-drop multiplexer, an analog phase modulator, an analog amplitude modulator, among others.
An optical device may include optical waveguides, diffraction gratings, optical lenses, and signal-processing elements. The optical waveguides direct an optical signal over the optical device. A diffraction grating decomposes the optical signal into its constituent spectral components. The constituent spectral components are converted into parallel beams by a collimating lens. Henceforth, the signal-processing elements manipulate the constituent spectral components. The signal-processing elements may include MEM switches, liquid crystal spatial light modulators, and so forth. Thereafter, a focusing lens converges the manipulated constituent spectral components to another diffraction grating. The diffraction grating combines the manipulated constituent spectral components into a processed optical signal.
A conventional optical device 100 used for waveform and wavelength modulation is illustrated in FIG. 1. Optical device 100 includes a first diffraction grating 102, an optical collimating lens 104, an array of signal-processing elements 106, an optical focusing lens 108, and a second diffraction grating 110. First diffraction grating 102 decomposes an input signal into a number of spatially separated beams according to their wavelengths. The spatially separated beams are also referred to as spectral component beams. After dispersion from first diffraction grating 102, the spectral component beams are collimated by optical collimating lens 104. Then, the spectral component beams enter into an array of signal-processing elements 106. The array of signal-processing elements 106 modulates the properties of the collimated spectral component beams such as optical amplitude and phase. Thereafter, the modulated spectral component beams are focused by optical focusing lens 108 towards second diffraction grating 110. Second diffraction grating 110 combines the focused spectral component beams into an output signal.
The components of optical device 100 are fixed at various positions in a three dimensional space and signal-processing element 106 is employed for signal manipulation. As a result, optical device 100 is relatively large in size. The large size of optical device 100 makes it difficult to integrate similar devices into optical communication and transmission devices.
In optical communication, an optical bit has a pulse length in nanoseconds. A typical data packet includes hundreds of optical bits and has a temporal length in microseconds. For processing a data-packet level or a bit-level signal, the signal processing element response time should be of the same order as the length of the signal. However, the response time of the signal-processing elements used in the conventional optical devices is in milliseconds. Further, the processing of signals is slower due to the size of the device as the signal has to travel larger distances. Therefore, conventional optical devices are not capable of conducting data-packet level and bit-level signal-processing. Their slow speed also limits the applicability of these optical devices to analog communication. Their large size leads to higher cost of manufacturing and lower device reliability.
In view of the above discussion, there is a need for an optical device that is compact, yet integrates discrete optical components and signal-processing elements. Further, the optical device should have a high processing speed to handle optical data packets and bit-level signals. Moreover, the optical device should have high spectral resolution and should be capable of modulating many constituent spectral components.